A new study that was recently conducted by researchers from the University of Rochester Environmental Health Sciences Center has revealed that exposure to hazardous chemicals such as DDT and PCBs can suppress a babies response to vaccines for tuberculosis.

The significance of these findings, which were recently published in the scientific journal Environmental Health Perspectives, is not only limited to an infants response to the TB vaccine; nor is it limited to exposure to the notorious two chemicals mentioned above. According to lead author, Dr Todd Jusko, who is an assistant professor in the departments of Environmental Medicine and Public Health Sciences at the University of Rochester:

"There are thousands of pollutants similar to PCBs and DDT with unknown health implications. Our work provides a foundation for how these types of chemicals affect the developing immune system in infants around the world."

For this study, the researchers focused on two key chemicals: polychlorinated biphenyls (PCBs); and DDE, which is the primary byproduct of the notoriously hazardous insecticide DDT. Both of these chemicals are considered extremely persistent pollutants as they do not readily break down in the environment, but rather persist to pose a health risk to both the environment and humans. Even though these chemicals were banned decades ago, they are still prevalent in the environment (notably soil and water) today.

TB Under the microscope

PCBs were routinely added to consumer products and other industrial products in the US until they were banned in 1979. But despite the ban, nearly everyone has detectable concentrations of PCBs in their blood — even people who reside in unindustrialized regions of the world. While DDT is now banned in the US, it is still in use in certain countries where malaria is a larger health issue. For this study, researchers took blood samples from 516 healthy moms and their infants living in eastern Slovakia — a region that is heavily polluted by environmental toxins — and assessed the immune responses of babies six months after being given a TB vaccine that was administered within four days of their birth.

They found that harmful chemicals were present in over 99% of the blood samples. However, babies with the highest PCB concentrations in their blood had fewer antibodies to fight off TB. Although the presence of DDE did not have such a strong influence on the levels of vaccine antibodies as PCBs, it still significantly reduced a baby's response to the TB vaccine; and babies that were exposed to both of these chemicals had the poorest immune response. PCB, DDE, and other persistent chemical toxins are able to pass through the placenta, and are also passed from mother's to their babies during breastfeeding. The authors note that a child develops his or her immune system in the early stages of life, and even the slightest changes can result in a dysfunctional immune system in the long-term. TB is a serious infectious killer disease that affected nearly 10 million people globally in 2014 alone. For years, scientists have pondered why people respond to the TB vaccine differently, with the impact that environmental toxins have on a child's developing immune system tending to be overlooked as a potential reason. This study shows that common environmental toxins can reduce the immune response to an important vaccine that is used globally to treat TB. Mothers (and their children) can be exposed to PCBs, DDT and other harmful environmental contaminants in drinking water.

Journal Reference Todd A. Jusko et al. A Birth Cohort Study of Maternal and Infant Serum PCB-153 and DDE Concentrations and Responses to Infant Tuberculosis Vaccination. Environmental Health Perspectives, December 2015 DOI: 10.1289/ehp.1510101